Method for transmitting and receiving additional control signals

ABSTRACT

A method for transmitting/receiving an additional control signal without any loss of bandwidth and power in an original Tx signal is disclosed. If the additional control signal is transmitted via the Tx signal composed of at least one of data and control signals, at least one of the amplitude and phase of the Tx signal of the time- and frequency-resource domain is modulated according to the additional control signal to be transmitted. The modulated Tx signal is transmitted to the receiver, so that the additional control signal can be transmitted irrespective of the original Tx signal. According to a modulation status of at least one of an amplitude and a phase of the Rx signal contained in the time- and frequency-resource domain, the additional control signal can be acquired.

TECHNICAL FIELD

The present invention relates to a method for transmitting/receivingadditional control signals without any loss of bandwidth and power in acommunication system having limited radio resources.

BACKGROUND ART

Generally, a broadband communication system has limited radio resources.In order to maximize the efficiency of radio resources, a variety ofmethods for effectively transmitting/receiving signals in a time-,space-, or frequency-domain and their utilization methods have beendeveloped.

Particularly, a multicarrier-based OFDM scheme reduces the complexity ofa receiver under frequency selective fading environments of a broadbandchannel, uses different channel characteristics of subcarriers, andperforms selective scheduling in a frequency domain, thereby increasingspectral efficiency. So, the multicarrier-based OFDM scheme has beenrecently focused to maximize the efficiency of radio resources in thefrequency domain.

In order to maximize the efficiency in a space domain, a Multi-InputMulti-Output (MIMO) technology is required, and several time andfrequency domains occur in the space domain, so that themulticarrier-based OFDM scheme transmits high-speed multimedia data.

In order to effectively use a time domain, the above-mentioned OFDMscheme performs channel encoding, performs scheduling based on channelselective characteristics of several users, and uses a HARQ schemeappropriate for transmission of packet data.

In order to implement a variety transmission/reception techniques fortransmitting broadband Space-Time high-speed packets, transmission ofdownlink/uplink control signals for time-, space-, and frequency-domainsis indispensable.

Under the above-mentioned environments, most conventional arts have beendesigned to use only radio resources of control channel pre-assigned fortransmission of control signals, so that the amount of overhead of thecontrol channels increases under broadband multi-user and multi-antennasenvironments, thereby reducing RF-channel capacity (e.g., a bandwidth)for actual data.

DISCLOSURE Technical Problem

Accordingly, the present invention is directed to a method fortransmitting and receiving additional control signals that substantiallyobviates one or more problems due to limitations and disadvantages ofthe related art.

An object of the present invention is to provide a method for generatingadditional control channels without any loss of bandwidth and power in aconventional transmission (Tx) signal during a transmission time ofcontrol signals, and transmitting control signals appropriate fordifferent Quality of Service (QoS) requirements over an additionalcontrol channel.

Another object of the present invention is to provide a method fordetermining whether data is contained in a conventional Tx signal, andeffectively transmitting/receiving additional control signals underdifferent channel structures, so that it can be applied to the differentchannel structures in various ways according to the determined result.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

Technical Solution

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, amethod for transmitting an additional control signal via a transmission(Tx) signal, the method comprising: modulating at least one of anamplitude and a phase of the Tx signal contained in a predeterminedtime- and frequency-resource domain according to the additional controlsignal; and transmitting the modulated Tx signal to a receiver, wherethe Tx signal comprises at least one of data and control signals, isprovided.

Preferably, the predetermined time- and frequency-resource domain isdetermined to be a domain which includes one or more frequency resourcesand one or more time resources according to reliability required for theadditional control signal.

Preferably, the amplitude and the phase of the Tx signal contained inthe predetermined time- and frequency-resource domain are modulatedaccording to the same additional control signal.

Preferably, at the modulating step, the Tx signal is modulated to havedifferent amplitudes or different phases according to the additionalcontrol signal.

Preferably, if the Tx signal comprises data and control signals, apredetermined first channel structure is used for transmission of the Txsignal; and if the Tx signal comprises only the control signal, apredetermined second channel structure is used for transmission of theTx signal. And, the predetermined time- and frequency-resource domain isdetermined according to the predetermined first and second channelstructures.

In another aspect of the present invention, there is provided a methodfor receiving a reception (Rx) signal, including an additional controlsignal, the method comprising: acquiring the additional control signalaccording to a modulation status of at least one of an amplitude and aphase of the Rx signal contained in a predetermined time- andfrequency-resource domain; compensating for the Rx signal using theacquired additional control signal; and acquiring transmission (Tx)signal information from the compensated Rx signal, when the Rx signalcomprises at least one of data and control signals.

Preferably, the predetermined time- and frequency-resource domain isdetermined to be a domain which includes one or more frequency resourcesand one or more time resources according to reliability required for theadditional control signal.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

The above-mentioned method for transmitting/receiving additional controlsignals according to the present invention generates additional controlchannels without any loss of frequency and power in a conventional Txsignal during a transmission time of control signals, transmits/receivesadditional control signals appropriate for different QoS requirementsover an additional control channel, and increases system performance.

And, the present invention determines whether data is contained in theconventional Tx signal, and can be applied to different channelstructures according to the determined result.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

In the drawings:

FIG. 1 is a block diagram illustrating a transmitter for transmittingmodulated additional control signals along with Tx signals according tothe present invention;

FIG. 2 is a block diagram illustrating a receiver based on additionalcontrol signals according to the present invention;

FIG. 3 shows additional control channels and resource structures oftime-, frequency-, and code-domains for use in Tx signals according tothe present invention;

FIG. 4 is a graph illustrating the relationship between the number ofbits capable of being transmitted over an additional control channel andthe number of unit samples used for demodulating a signal equipped withadditional control signals according to the present invention;

FIG. 5 shows a constellation created when a Tx signal is BPSK-modulatedand the modulated Tx signal is then modulated by additional controlsignals according to the present invention;

FIG. 6 shows a phase range which is changeable by additional controlsignals when a method for modulating an original Tx signal is a BPSK;

FIG. 7 shows a phase range which is changeable by additional controlsignals when an original Tx signal is modulated by a M-ary QAM accordingto the present invention;

FIG. 8 is a block diagram illustrating a method for transmittingadditional control signals when data and control signals aresimultaneously transmitted according to the present invention;

FIG. 9 shows a channel structure used when only uplink control signalsare transmitted according to the present invention; and

FIGS. 10˜11 show a method for transmitting additional control signalsaccording to a FDM or CDM scheme when only uplink control signals aretransmitted according to the present invention.

BEST MODE

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

Prior to describing the present invention, it should be noted that mostterms disclosed in the present invention correspond to general termswell known in the art, but some terms have been selected by theapplicant as necessary and will hereinafter be disclosed in thefollowing description of the present invention. Therefore, it ispreferable that the terms defined by the applicant be understood on thebasis of their meanings in the present invention.

For the convenience of description and better understanding of thepresent invention, general structures and devices well known in the artwill be omitted or be denoted by a block diagram or a flow chart.Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to the same or like parts.

The present invention relates to a method for generating a channel foradditional control signals in association with Tx resources of time-,frequency-, and code-domains, and transmitting/receiving additionalcontrol signals over the generated channel. Amplitudes and phases forthe additional control signals forming the additional control signalchannels are represented by the following equation 1:

s _(c) =a _(c) exp(jθ _(c))   [Equation 1]

Equation 1, s _(c) is an additional control signal, a_(c) is anamplitude of the additional control signal, and θ_(c) is a phase of theadditional control signal.

In the meantime, the phase of the additional control signal can bedetermined by various modulation methods of the Tx signal. Provided thata M-ary PSK signal is transmitted, an available phase variation can berepresented by the following equation 2:

$\begin{matrix}{{\theta_{c} = {\frac{\pi}{M}\left( {\frac{{2k} + 1}{M_{c}} - 1} \right)}},{k = 0},1,\ldots \mspace{14mu},M_{c}} & \left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack\end{matrix}$

In Equation 2, additional control signal information can be indicated bythe variable M_(c), and “M” in the equation 2 represents the modulationorder of M-ary PSK.

FIG. 1 is a block diagram illustrating a transmitter for transmittingmodulated additional control signals along with the other signals to betransmitted according to the present invention.

In more detail, the modulated additional control signal having theamplitude and the phase of Equations 1 and 2 is multiplied by othertransmission signals, in a multiplication module 101. In this case, theother transmission signals may be data, control signal, or both of them,as shown in FIG. 1. And, if the additional control signal is multipliedby the other transmission signals, this case indicates that theamplitude and phase of the transmission signals are modulated by theadditional control signal.

In the meantime, the above-mentioned resultant signal created when theadditional control signal is multiplied by the transmission may beproperly mapped to radio resources of time-, frequency-, andcode-domains by the time-/frequency-/code-domain multiplexing/spreadingmodule 102, so that the mapping result may be then transmitted. In thiscase, an additional channel generation method is changed to anothermethod according to a multi-user access method or Tx-signal multiplexingmethod based on FDM-, CDM-, and TDM-schemes. Detailed access methods ofdifferent additional channel generation methods will hereinafter bedescribed. In the meantime, a method for receiving the above-mentionedTx signal will hereinafter be described.

FIG. 2 is a block diagram illustrating a receiver based on additionalcontrol signals according to the present invention.

FIG. 2( a) shows a coherent-modulation-based receiver, which applieschannel information to a control-channel resource unit via which anadditional control channel is transmitted. FIG. 2( b) shows anon-coherent-based receiver, which demodulates desired data withoutusing channel information.

Referring to FIG. 2( a), if reception (Rx) signals (e.g., data, controlsignal, or both of them) are coherent-demodulated, thedemultiplexing/despreading module 211 of the receiver acquires the Rxsignals from a time-, frequency-, or code-domain. A pilot or a referencesignal (RS) from among the acquired Rx signals is used to performchannel estimation by the channel estimation module 212. The estimatedchannel value compensates for channel fading of Rx signals by theequalization/despreading module 213. The compensated Rx signals enterthe additional control signal acquisition step by the additional controlsignal demodulation module 214. The multiplication module 215 removesthe influence of additional control signals from Rx signals using theacquired additional control signals. The coherent-demodulation module216 performs general coherent demodulation, so that it can acquire Rxsignal information.

Referring to FIG. 2( b), if Rx signals (e.g., data, control signal, orboth of them) are non-coherent-demodulated, thedemultiplexing/despreading module 221 of the receiver acquires the Rxsignals from the time-, frequency-, or code-domain. But, thenon-coherent receiver of FIG. 2( b) does not perform the channelestimation differently from FIG. 2( a), the blind detection module 222performs blind detection using samples of the demultiplexed/despread Rxsignals, so that the additional control signals are recovered.Thereafter, the recovered additional control signal enters themultiplication module 223, so that the multiplication module 223 removesthe influence of additional control signals from the Rx signals, and theresultant Rx signals are applied to the non-coherent demodulation module224, so that the non-coherent demodulation module 224 performs generalnon-coherent demodulation, thereby acquiring Rx signal information.

In the meantime, the present invention modulates the transmission signalover the generated additional control channel, and transmits additionalcontrol signals. The present invention modulates at least one ofamplitude and phase of each Tx signal in time- and frequency-domains,and multiplies the additional control signal having specific amplitudeand phase by the Tx signal of the time- and frequency-domains.Preferably, the above-mentioned time- and frequency-domain may bedetermined to be a domain composed of at least one frequency resourceand at least one time resource according to different QoS requirementsof the Tx additional control signal.

The above-mentioned method for generating the additional control signal,mapping the generated additional control signal to a resource domain,and transmitting the mapping result will hereinafter be described.

FIG. 3 shows additional control channels and resource structures oftime-, frequency-, and code-domains for use in Tx signals according tothe present invention.

In order to explain the resource structure of FIG. 3, parameters (i.e.,D_(f), D_(t), S_(f), and S_(t)) of FIG. 3 can be defined as follows.

D_(f) is the number of frequency-domain resources via which additionalcontrol channel information is transmitted, for example, the number ofsub-carriers, the number of frequency channels, and the number offrequency groups.

D_(t) is the number of time-domain resources via which additionalcontrol channel information is transmitted, for example, the number ofTx symbols, the number of slots, and the number of frames.

S_(f) is a frequency-domain spreading factor for transmittingdata/control signals.

S_(t) is a time-domain spreading factor for transmitting data/controlsignals.

In this case, it is preferable that D_(f) be set to an integer multipleof the frequency-domain spreading factor to which the same additionalcontrol signal is applied, as represented by D_(f)=k_(f)*S_(f). It ispreferable that D_(t) be set to an integer multiple of the time-domainspreading factor to which the same additional control signal is applied,as represented by D_(t)=k_(t)*S_(t).

The above-mentioned resource structure may include all Tx structuresbased on FDM-, CDM-, and TDM-schemes, and an arbitrary Tx-resourcestructure may generate additional control channels. The additionalcontrol signal can be applied to the above-mentioned FDM-, CDM-, andTDM-schemes in various ways. For example, there are four applicationcases 1)˜4), and their detailed description will hereinafter bedescribed.

1) FDM/TDM-based transmission structure (including a single-carrierstructure): S_(f)=S_(t)=1

2) Frequency-domain CDM: S_(f)≠1, S_(t)=1

3) Time-domain CDM: S_(f)=1, S_(t)≠1

4) Various combination structures of Cases 1)˜3)

In more detail, the additional control signal modulated by Equation 1converts an amplitude and/or a phase of a Tx signal (e.g., data and/orcontrol signal), and is mapped to a resource domain having the samestructure as FIG. 3, so that the mapping result is finally transmitted.If the amplitude and/or the phase of the Tx signal contained in theresource domain having the magnitude of D_(f) and D_(t) are/ismodulated, the additional control signal may be represented by themodulated result.

In the meantime, the above-mentioned method for generating an additionalchannel by converting the phase and/or the amplitude of the Tx signalcan be implemented in different ways according to the FDM or CDM scheme.

If the frequency- and time-domain spreading factor of the Tx signal isset to “1” according to the FDM scheme, the FDM scheme performssymbol-level modulation of the Tx signal used as the data/control signalin each frequency unit, so that the additional control signal can berepresented by the modulated result. Otherwise, the CDM scheme maymodulate several symbols of the time or frequency domain into othersymbols according to the spreading factor of the Tx signal.

Therefore, the resource structure for allocating the additional controlsignal according to the embodiment shown in FIG. 3 can flexibly performresource allocation to construct the additional channel, and is able todetermine the amount of data capable of being transmitted over theadditional control channel.

However, the demodulation method of the additional control channel isperformed using individual samples on the basis of a domain composed ofD_(f) and D_(t) in the additional control channel resource structure. Asthe number of samples increases, the reliability of the additionalcontrol channel also increases, so that a trade-off relationship betweenthe Tx capacity and the number of samples of the additional channel unitis made. In the present invention, the term “sample” is a signal unittransmitted to a domain composed of both a single frequency resource anda single time resource.

In more detail, provided that N_(f) is the number of all transmittablefrequency-domain resources and N_(t) is the number of time-domainresources contained in a symbol-unit transmission time interval (TTI),the number of bits transmittable over the additional control channel ina single TTI can be represented by the following equation 3:

$\begin{matrix}\begin{matrix}{R_{bit} = {\left\lfloor \frac{N_{f}N_{t}}{D_{f}D_{t}} \right\rfloor \log_{2}M_{c}}} \\{= {\left\lfloor \frac{N_{f}N_{t}}{\kappa_{f}\kappa_{t}S_{f}S_{t}} \right\rfloor \log_{2}M_{c}}} \\{= {\left\lfloor \frac{N_{f}N_{t}}{N_{s}S_{f}S_{t}} \right\rfloor \log_{2}M_{c\;}}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

In Equation 3, N_(s) is the number of samples capable of being used todemodulate a control signal which has been transmitted over theadditional control channel.

Based on the relationship between the number of bits transmittable overthe additional control channel and the number of unit samples used todemodulate a signal including additional control signals, a method fordetermining the resource domain to transmit the additional controlsignal will hereinafter be described in detail.

FIG. 4 is a graph illustrating the relationship between the number ofbits capable of being transmitted over an additional control channel andthe number of unit samples used for demodulating a signal equipped withadditional control signals according to the present invention.

In more detail, it is assumed that a signal is QPSK-modulated under theOFDM environment and the QPSK-modulated result is then transmitted, sothat the relationship between the number of bits of a control signaltransmittable over the additional control channel and the number ofsamples used to demodulate the control signal is depicted in FIG. 4.Specifically, the result of FIG. 4 is acquired under the OFDMenvironment in which the number (N_(f)) of all frequency resources is2048, the number (N_(t)) of all time resources is 12, and thefrequency-domain spreading factor (S_(f)) of the Tx signal is 16.

As can be seen from FIG. 4, the channel construction can be flexiblymade according to the number of bits required for transmitting theadditional control signal, and the number of samples may also be changedto another number according to requirements of the control signal.Therefore, the method for transmitting the additional control channelsignal according to the present invention can determine domains (i.e.,the number of samples to which the same additional control signal isapplied) for modulating the amplitude/phase of the Tx signal accordingto unique reliabilities required for individual QoS control signals. Asa result, the present invention can flexibly design a channel accordingto unique Tx capacity and unique Tx reliability for each control signal.

In the meantime, the above-mentioned method for modulating the Txsignal, mapping the modulated result to the time-, frequency-, andcode-domain resources, and detecting a desired signal upon receiving themapping result will hereinafter be described in detail.

In order to recover the Tx signal which has transmitted over theadditional control channel, the present invention requires the coherentor non-coherent access method according to the demodulation method ofthe amplitude- and/or phase-modulated signal of the above-mentionedadditional control signal

The coherent-demodulation-based receiver shown in FIG. 2( a) can acquirechannel information from the time- or frequency-domain via a pilot or RS(reference signal), and reduce the time/frequency selective fadingeffect of the Rx signal, thereby increasing the reliability of samplesused for demodulating the additional control signal. Therefore, if theadditional control channel is generated and applied to a resourcestructure at which the data signal arrives. Generally, the receiver ofFIG. 2( a) can perform channel estimation using the pilot or RS, so thatit is preferable that the additional control signal be recovered by thecoherent demodulation scheme.

The non-coherent-demodulation-based receiver shown in FIG. 2( b) hasdifficulty in compensating for the time/frequency selective fading inthe Rx signal by acquiring channel information. The additional controlsignal must be recovered using samples acquired by demultiplexing ordespreading the Rx signal. However, as shown in FIG. 3, the presentinvention applies the same additional control signal to a Tx signalcontained in a predetermined time- and frequency-domain, and transmitsthe applied result, so that the above-mentionedtime-/frequency-selective fading effect can be reduced. In other words,the present invention can establish the variable D_(f) within a coherentbandwidth in consideration of a delay spread encountered by multi-pathcharacteristics of a RF channel. And, the present invention canestablish the variable D_(t) within a coherent time in consideration ofDoppler characteristics caused by user's mobility. As a result, thepresent invention can perform blind detection using N_(s) samplescontained in the time- and frequency-domains. In this case, N_(s) is thenumber of samples contained in D_(f)*D_(t), and may be set to “1”according to the reliability required for the control signal.Specifically, if the additional control signal is transmitted via thecontrol signal composed of spreading codes (e.g., SCH), the presentinvention can detect the additional control signal from a single sampleusing the despreading, so that it can determine an appropriate receiverstructure according to the type of original Tx data.

According to the above-mentioned method for detecting the coherent ornon-coherent additional control signal, a variety of methods fordetecting a phase and its amplitude variation on the basis of severalsamples generated from either original Tx data or control signals arerequired. For example, Mc number of candidate constellation points aregenerated using a Geometric clustering algorithm (e.g., a K-means (ormedoids) algorithm or, QT-clustering algorithm), and are compared withother constellation points capable of being actually transmitted, sothat the phase variation can be estimated according to the comparisonresult. As a result, the additional control channel signal from the Rxsignal can be demodulated according to the above-mentioned method.

If there is a different demodulation technique in the original Tx signalcorresponding to samples contained in the frequency- and time-domains towhich the same additional control channel of FIG. 3 is applied, a phaseof the additional control signal is determined as described above. Aftera demodulator performs the above-mentioned recovery method associatedwith the same modulation method, it calculates the sum of weightedvalues of the distances between each candidate constellation point andeach transmittable constellation point, so that the additional controlchannel signal can be determined according to the comparison result ofthe weighted values. In this case, the weighting factor may bedetermined by the number of samples contained in a specific area towhich the same modulation scheme is applied.

The above-mentioned algorithm for detecting the additional controlsignal will hereinafter be described in detail.

According to the present invention, the receiver, which has received theTx signal having the amplitude and/or phase modulated by the additionalcontrol signal, estimates the amplitude and/or the phase of the Rxsignal, so that the present invention provides a method for recoveringthe additional control signal using the above-mentioned receiver. Inother words, the present invention performs constellation demapping toacquire the additional control signal from the Rx signal, and removesthe influence of the acquired additional control signal from the Rxsignal, thereby acquiring information of the original Tx signal from theresultant Rx signal.

FIG. 5 shows a constellation created when a Tx signal is BPSK-modulatedand the modulated Tx signal is then modulated by additional controlsignals according to the present invention.

In more detail, the constellation of FIG. 5 is made when the amplitudeof the additional control signal represented by Equation 1 is set to “1”and its phase is 30°. Namely, if there is no variation in the amplitudeof the Tx signal and only the phase rotates by 30°, the constellation ofFIG. 5 is made.

As described above, the transmitter according to the present inventiondoes not transmit information of the amplitude (a_(c)) and informationof the phase (θ_(c)) shown in Equation 1 to the receiver. As can be seenfrom FIG. 5, the receiver receives a signal different from the knownBPSK constellation, so that the receiver must estimate amplitude/phasevariation information caused by the additional control signal withoutassistance of the transmitter. There is no variation in the amplitude(i.e., a_(c)=1) in FIG. 5, but there is a variation in the phase, sothat the constellation of FIG. 5 is rotated as compared to theconventional BPSK constellation, so that the rotation degree must beestimated.

However, in order to estimate the above-mentioned rotation degree, theaccurate value of each Rx signal must be recognized. Therefore, in orderto acquire the above-mentioned variation amount, the following techniquecan be used.

The present invention does not know category information of each Rxsignal, such that it groups individual signals by referring to agrouping format of constellation coordinates on a constellation map, andmaps each group to a constellation of original signals. As a result, thepresent invention can acquire the amplitude and phase information addedby the additional control signal. In other words, according to thepresent invention, the additional control signal can be commonly appliedto the Tx signal contained in the frequency- and time-domain(D_(f)*D_(t)), so that a common constellation and variation informationcaused by the additional control signal applied to the commonconstellation can be estimated using samples contained in the frequency-and time-domain (D_(f)*D_(t)).

In the meantime, the constellation coordinates caused by the Txmodulation based on the additional control signal according to thepresent invention may be contained in a predetermined range in whichconstellation coordinates of the original Tx signal can bediscriminated.

FIG. 6 shows a phase range which is changeable by additional controlsignals when a method for modulating an original Tx signal is a BPSK.

In FIG. 6, “600” and “630” are constellation coordinates to which theoriginal Tx signal is mapped according to the BPSK modulation scheme.And, “601” and “631” are constellation coordinates formed when theconstellation coordinates of the original Tx signal are rotated by theadditional control signal.

In FIG. 6( a), the constellation coordinates of the original Tx signalare rotated by the additional control signal. In FIG. 6( b), if theinfluence of the additional control signal is removed from the receiver,the constellation coordinates of the Rx signal rotated by the additionalcontrol signal is restored to the constellation coordinates of theoriginal Tx signal.

In this way, if the original Tx signal is BPSK-modulated, the phaserotation caused by the additional control signal may be determined in apredetermined range in which the original Tx signal can bediscriminated, i.e., the range from −90° to 90°.

FIG. 7 shows a phase range which is changeable by additional controlsignals when an original Tx signal is modulated by a M-ary QAM accordingto the present invention.

In FIG. 7, “640” is one of constellation coordinates created when the Txsignal is modulated by the M-ary QAM scheme, and “641” is a specificformat on which the coordinates of 640 are phase-rotated by theadditional control signal. In the same manner as in FIG. 6, FIG. 7( a)shows that the constellation coordinates of the original Tx signal arephase-rotated by the additional control signal, and FIG. 7( b) showsthat the constellation coordinates of the Rx signal phase-rotated by theadditional control signal is restored to the constellation coordinatesof the original Tx signal when the influence of the additional controlsignal is removed from the phase-rotated Tx signal.

In this way, if the original Tx signal is modulated by the M-ary QAMscheme, the phase rotation caused by the additional control signal canbe determined in a predetermined range in which the original Tx signalcan be discriminated, i.e., the range from −180/M° to 180/M°.

The present invention effectively transmits the additional controlsignals without any loss of bandwidth and power in the original Txsignal composed of data and/or control signals, establishes variablefrequency- and time-domains according to the reliability required forindividual control signals, and modulates the Tx signal contained in acorresponding domain according to the additional signal, so that themethod for transmitting the additional control signal can beappropriately applied. As shown in FIG. 3, the present invention candesign the additional control signals to have a variety of resourcestructures, so that it can be applied to a variety of channel structuresaccording to the original Tx signal.

The method for transmitting/receiving the additional control signalaccording to the present invention may be applied to the 3GPP LTE uplinkchannels in various ways, and associated embodiments will hereinafter bedescribed in detail.

In accordance with one embodiment of the present invention, the SC-FDMscheme can effectively transmit the concentrated Tx power over the 3GPPLTE uplink, and can reduce the PAPR of the power variation of the OFDMsignal. Under this configuration, the control signal can be transmittedin two methods, i.e., a first method 1) and a second method 2).According to the first method 1), the signal are simultaneouslytransmitted. According to the second method 2), only the control signalis transmitted. The method for applying the above-mentioned additionalcontrol signal transmission method to the first and second methods canbe implemented in different ways.

FIG. 8 is a block diagram illustrating a method for transmittingadditional control signals when data and control signals aresimultaneously transmitted according to the present invention.

Referring to FIG. 8, if the data and the control signals aresimultaneously transmitted as Tx signals, the phase and/or the phase ofthe Tx signal are/is changed by the additional control signal denoted byEquation 1, and the changed result can be transmitted according to theSC-FDM scheme. In more detail, the multiplication module 801 maymodulate the amplitude and/or phase of the Tx signal including the dataand control signals according to the additional control signal. Theamplitude-modulated and/or phase-modulated Tx signals are converted intoparallel signals by the serial/parallel (S/P) converter 802. Then, theSC-FDM is performed by the DFT module 803 and the IFFT module 804, sothat the SC-FDM result may be transmitted via the uplink.

In this case, all or some of control signals to be transmitted may alsobe transmitted as the additional control signals.

As described above, in the above-mentioned embodiment for transmittingthe additional control signals along with the data and control signals,provided that the original Tx signal may be composed of the FDM(S_(f)=S_(t)=1), and the additional control channel is transmitted tothe 20 MHz bandwidth via a single resource block (RB) (D_(f)=12) duringa TTI of 1 msec (D_(t)=14), the additional control signal composed ofk_(RB)*log(M_(c)) bits can be transmitted via the k_(RB) number ofresource blocks (RBs). In other words, the present invention can detecta single additional control signal using 144 samples (i.e., 12*(14−2);except for two RSs) contained in the aforementioned frequency- andtime-domains.

In this way, if the additional control signal is demodulated by asufficient number, of samples, the reliability of the Tx signal can begreatly increased. Therefore, the present invention is advantageous totransmission of the control signal (e.g., ACK/NACK) which requires alower error rate as compared to a CQI (Channel Quality Indicator) orPMI.

In the meantime, if the additional control signal transmission method isapplied to the channel structure created when only the control signalother than data is transmitted as the original Tx signal, a detaileddescription will hereinafter be described.

FIG. 9 shows a channel structure used when only uplink control signalsare transmitted according to the present invention.

Referring to FIG. 9, if only the 3GPP LTE uplink transmits only thecontrol signal, the user equipment (UE) may receive one or both ends ofthe system bandwidth to transmite the control signal. Therefore, acorresponding UE forms the control signal to be transmitted within theallocated bandwidth according to the SC-FDM scheme, and transmits theformed control signal. In order to transmit the additional controlsignal to the channel, the present invention can perform the FDM- orCDM-formatted access.

FIGS. 10˜11 show a method for transmitting additional control signalsaccording to a FDM or CDM scheme when only uplink control signals aretransmitted according to the present invention.

As shown in FIG. 10, if the additional control signal is transmittedaccording to the FDM scheme, two successive sub-channels are used as abasic unit for transmitting the additional control signal, and a singleadditional control signal is transmitted according to the basic unit fortransmitting the additional control signal. If necessary, theabove-mentioned FDM scheme assigns several control channels, so that asingle additional control signal can be transmitted.

In more detail, provided that the original Tx control signal istransmitted via 6 control channels within a single RB as shown in FIG.10, and a basic unit for the additional control channel application is asingle RB (i.e., 1RB; D_(f)=12) and a single TTI (i.e., 1TTI; 14symbols; D_(t)=14), the additional control signal of log(M_(c)) bits canbe transmitted via the 1RB, and a single additional control symbol canbe detected via 96 samples (12*(14−6); except for 6 RS symbols).

In this way, if the time-domain spreading code is applied to the FDMformat, the number of samples for recovering the additional channelsignal is reduced, but the reliability increases by a time-domainaverage value of each sample, so that the additional channel signal canbe recovered.

In the meantime, if the additional control signal is transmittedaccording to the CDM scheme, the additional control signal istransmitted as shown in FIG. 11. In more detail, the spreading code(e.g., a Zadoff-Chu (ZC) sequence) characteristics are applied to thepre-allocated control channel of the frequency domain. In the samemanner as in the FDM scheme, the same additional control signal istransmitted to the basic resource unit for transmitting the additionalcontrol channel, so that the control signal can be transmitted to adestination without using an additional bandwidth and power request.

The method for generating the additional control channel andtransmitting the additional control signal using the generatedadditional control channel can be flexibly applied to a Multi-InputMulti-Output (MIMO) environment requiring transmission of severalACK/NACK signals, thereby reducing an amount of overhead in each controlsignal.

If there is no Tx control signal for the additional control channel, thedata signal can be transmitted, and the frequency efficiency increases,thereby increasing the amount of Tx data.

It should be noted that most terminology disclosed in the presentinvention is defined in consideration of functions of the presentinvention, and can be differently determined according to intention ofthose skilled in the art or usual practices. Therefore, it is preferablethat the above-mentioned terminology be understood on the basis of allcontents disclosed in the present invention.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

INDUSTRIAL APPLICABILITY

As apparent from the above description, according to the above-mentionedmethod for transmitting/receiving additional control signals, thepresent invention generates additional control channels without any lossof frequency and power in a conventional Tx signal during a transmissiontime of control signals, transmits/receives additional control signalsappropriate for different QoS requirements over an additional controlchannel, and increases system performance. The scope or spirit of thepresent invention is not limited to only the system disclosed in theabove-mentioned description, and can also be applied to a variety ofwireless communication systems.

Although the preferred embodiments of the present invention have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the inventionas disclosed in the accompanying claims.

1. A method for transmitting an additional control signal via atransmission (Tx) signal, the method comprising: modulating at least oneof an amplitude and a phase of the Tx signal contained in apredetermined time- and frequency-resource domain according to theadditional control signal; and transmitting the modulated Tx signal to areceiver, wherein the Tx signal comprises at least one of data andcontrol signals.
 2. The method according to claim 1, wherein thepredetermined time- and frequency-resource domain is determined to be adomain which includes one or more frequency resources and one or moretime resources according to reliability required for the additionalcontrol signal.
 3. The method according to claim 2, wherein theamplitude and the phase of the Tx signal contained in the predeterminedtime- and frequency-resource domain are modulated according to the sameadditional control signal.
 4. The method according to claim 1, wherein:at said modulating, the Tx signal is modulated to have differentamplitudes or different phases according to the additional controlsignal.
 5. The method according to claim 1, wherein: if the Tx signalcomprises data and control signals, a predetermined first channelstructure is used for transmission of the Tx signal, and if the Txsignal comprises only the control signal, a predetermined second channelstructure is used for transmission of the Tx signal, and thepredetermined time- and frequency-resource domain is determinedaccording to the predetermined first and second channel structures.
 6. Amethod for receiving a reception (Rx) signal, including an additionalcontrol signal, the method comprising: acquiring the additional controlsignal according to a modulation status of at least one of an amplitudeand a phase of the Rx signal contained in a predetermined time- andfrequency-resource domain; compensating for the Rx signal using theacquired additional control signal; and acquiring transmission (Tx)signal information from the compensated Rx signal, wherein the Rx signalcomprises at least one of data and control signals.
 7. The methodaccording to claim 6, wherein the predetermined time- andfrequency-resource domain is determined to be a domain which includesone or more frequency resources and one or more time resources accordingto reliability required for the additional control signal.